DE2063672A1 - Process for the production of titanium dioxide - Google Patents

Description

DR. E. WIEGAND DIPL-ING. W. NiEMANN 2063672

DR. M. KOHLER DIPL-ING. C. GERNHARDT

MÖNCHEN HAMBURG

555476 800Q monks is, ²⁴ · December 197C

TELEGRAMS; KARPATEMF NUSSBAUMSTRASSE 10

W. 40268/70 -Eo / Ke

Laporte Industries Ltd. London, England

Process for the production of titanium dioxide

The invention is concerned with the manufacture of pigmentary titanium dioxide.

A titanium dioxide suitable for use as a pigment can be produced by hydrolysis of a solution of a titanium compound, for example the solution obtained in the sulfation of ilmenite, and subsequent calcination of the similar material

obtained hydrolyzate, which contains hydrous titanium dioxide to develop pigmentary properties will. The process can be carried out so that the titanium dioxide formed is in the crystallographic form either the anatase or the Rufeil is present.

The more important pigmentary properties include lightness, opacity, and texture and have been various proposals have already been made to improve these properties. Di3 '/ approve any suggestions

109837/1626.

BATH ORIGINAL

generally precalcination treatments of the various types. For example, in British Patent 84-6 085 describes a "method in which a obtained by hydrolysis of a solution of titanium sulfate Titanium dioxide hydrolyzate is washed with ammonia or an alkaline ammonium compound is neutralized, a further wash 2 to remove the in the neutralization stage ammonium sulfate formed is subjected and then calcined so that the pig ™ mental! titanium dioxide results. That when washing for removal of the ammonium sulfate used is before the ™ Use practically free of calcium and magnesium ions fc, however, is based on the incorporation of a water-insoluble zinc compound into the hydrolyzate prior to galvanization claims an increase in the coloring power of the pigment obtained »

It has been a common feature of pre-calcination neutralization treatments so far, that the soluble salts formed during neutralization or otherwise are removed by washing before calcination, and it has been suggested that the removal of soluble sulfates, e.g. the neutralization of the titanium dioxide hydrolyzate

»Were, during washing, through the incorporation of compounds -

fertilize elements containing insoluble oxides, hydroxides, Form carbonates or basic carbonates, in which hydrolyzate is supported »Examples of such elements, that have been suggested include cadmium, lanthanum, cerium, zirconium, thorium, niobium, tantalum, and antimony.

The invention provides a method of making pigmentary titanium dioxide, which consists of a Solution of titanium sulfate to precipitate water-containing Titanium dioxide is hydrolyzed, a rutile

109137/1626

BATH ORIGINAL

Formation-promoting inoculum is incorporated into the solution of the titanium sulfate and / or into the precipitate is washed, the precipitate and the washed precipitate with one or more treating agents the group of lithium, beryllium, aluminum, magnesium, zinc, sodium, potassium, cubidium, cesium and compounds of these metals is treated, the precipitate with a total amount of at least 0.7% by weight of an ammonium compound or more ammonium compounds, calculated as ammonium sulfate and based on the weight of the titanium dioxide, is treated, then the precipitate is calcined and the pH value of the moist precipitate in the range from 6 to 10 immediately before CaI-cinierung is held, the calcination being carried out at a temperature in the range from 750 to 1000 ° C

₁ and pigmentary titanium dioxide is obtained and the amount of the treatment agent or agents is such that in the precipitate immediately before calcination a total amount of the agent or agents from the group of beryllium, aluminum, magnesium, zinc and compounds of these metals, the amount of the agent or agents is calculated as metal oxide, within the range from 0.02 to 0.50% by weight and based on the weight of the titanium dioxide, and a total amount is present in the precipitate immediately before calcination on one or more agents from the group of sodium, potassium, rubidium, cesium, and compounds of these metals, wherein the amount of or the center is calculated as alkali metal oxide, based on the weight of the titanium dioxide _/ is present within the range of 0.05 to 1.0 wt.%, with lithium and / or one or more lithium compounds instead of any or all of the treatment agent or agents from the first listed eil and / or the second group can be used «

109837/1626

That obtained by the process according to the invention Titanium dioxide pigment has superior brightness, opacity and / or texture when compared to the after titanium dioxide pigments obtained by conventional methods.

The total amount of the treatment agent or agents can be added to the precipitate either before or after any necessary pH adjustments have been made can be incorporated. On the other hand, amounts of the treatment agent or agents can be used in the precipitate incorporated before as well as after such a pH adjustment be, with the only prerequisite, - that the entire portion of the treatment agent or the ■

means of action in the precipitate immediately before the calcination is within the suitable range given above. Of course Some of the treatment agents themselves can have some influence on the pH of the wet precipitate own.

The concentration of any impurities in the _c

Precipitation, such as B. Iron, Vanadium and Chromium, Jg should be:

at or below an acceptable maximum value, at- i

episodes below 50 parts per million (ppm) in the case of iron and at or below 3 ppm in the case of vanadium and chromium before the treatment and pH adjustment steps are carried out. Palis these impurities remain together with the titanium during the following treatment steps, the resulting titanium dioxide pigment becomes discolored due to the presence of the compounds of the impurity elements. The washing of the precipitate serves to remove at least some of these impurities and also to wash out a part the sulfuric acid remaining after hydrolysis. However, it can increase the concentration of the impurities to degrade that to an acceptable value

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• BATH

Washing stage with an acid treatment. add to. It is also possible, the amount of any chromium and vanadium impurities initially present in the precipitate by performing a pre-hydrolysis purification treatment, e.g. B. in the. Provisional Specification of application 60068/69 is proposed.

For various reasons it is unfavorable to try to remove the contaminants by washing the precipitate after it has been subjected to the treatment and pH adjustment according to the invention. First ' such washing changes the state of flocculation of the precipitate and thereby the properties, for example texture and undertone, ultimately pigment obtained on calcination deteriorated. In the extreme case, the state of flocculation can occur can be changed to such an extent that peptization occurs and this occurs particularly easily when the pH of the precipitate is adjusted to a value in the region of the higher end of the specified range became. Second, there is a considerable risk that at least some of the soluble treatment agents, which are incorporated in the precipitate are removed by this washing, and this would be necessary make up the precipitate with the treatment agent supplement so that the amount of this agent present in the precipitate immediately before calcination is within of the above suitable range. Thirdly, at least some of the existing ammonium compound or compounds removed and by this removal the total amount of existing Ammonium compound or compounds below 0.7% by weight, calculated as ammonium sulfate and based on the weight of the titanium dioxide, drop off. It would then be necessary

109837/1826

agile, another lot of. Ammonia or an ammonia compound incorporated into the precipitate and with this further addition there is again the danger the increase in the pH of the precipitate above the specified maximum.

Although it is unfavorable, the precipitation of dex · treatment stage and wash of any necessary pH adjustment step, the excess liquid from the Niederschlag.unmittelbar before Oalcinierung may, in spi elsweise augmentation by Filtri werdea from ₉ ■ when th e

fe advertising the ammonium compounds and the Beliandlimgsmittel or the treatment agent before calcination within the specified areas are kept «

The or each treatment agent has to be ordered in advance from a compound of one of these metals and preferably from a water-soluble compound. Water-insoluble While compounds can be used, these compounds must be thoroughly precipitated be mixed in if good results are to be achieved «. This mixing canoe by means of a mixer with a high shear rate, for example a Frerikel screw.

The connections in the first group can be simple

P be salts, for example sulfates, chlorides or nitrates, basic salts, for example oxychlorides or basic Sulfates, bases, for example oxides or hydroxides, salts of organic acids, for example formates, Acetates or oxalates, or organometallic compounds, for example meballalkyls or alkoxides »Advantageously the compound from the first group becomes an aqueous one Slurry added to the precipitate and they is preferably added in the form of an aqueous solution. The total proportion of the treatment agent is preferably

09837 / 162-8 -

BATH ORIGINAL

means or the treatment agent from the first listed Group present in the precipitate immediately before calcination, in the range from 0.02 to 0.2% by weight, calculated as metal oxide or oxides and based on the weight of the iELtane dioxide.

The connections of the broader group can consist of simple Salts, for example sulfates, nitrates or chlorides, basic compounds, for example oxides, Hydroxides, carbonates or bicarbonates, salts of organic acids, for example acetates, oxalates or Benzoates or organometallic compounds, such as alkoxides, exist. Preferably there is the connection or Each compound from the second group listed a sodium compound. As in the case of the compounds from the first group, the compounds from the second Group also advantageously to an aqueous one Added slurry of the precipitate and are preferably added in the form of an aqueous solution.

The total proportion of the treatment agent is preferred or the treatment agent from the second group listed, that in the precipitate immediately before calcination is present, in the range from 0.1 to 0.6% by weight, calculated as alkali oxide or oxides.

The lithium compound or any lithium compound J

can and will consist of any of the compounds listed above with respect to the second group advantageously to an aqueous suspension of the precipitate and preferably in the form of an aqueous solution added.

An advantageous embodiment of the invention Method is the one where the only treatment agent or agents used of lithium and / or one or more

109837/1676

Idthium compounds exist.

The treatment agent or agents can be used in the precipitate by adding an aqueous mixed solution of the agent or agents to an aqueous slurry of the precipitate to be admitted »

In general, the pH of the wet precipitate does not fall within the specified range the washing stage and there will be a pH adjustment necessary ..

Any pH adjustment is advantageous at least partially carried out in that the ammonium compound is an alkaline ammonium compound, for example ammonium hydroxide or ammonium carbonate is used. However, if the one before calcination existing requirements with regard to the pH value and with regard to the total proportion of the ammonium compound or compounds and the treatment agent or agents are met, the pH adjustment can at least in part by means of any alkaline Be effected by means. So z. B. the pH of the wet precipitation to a value slightly below 6 can be increased by treatment with ammonia or an alkaline ammonium compound, whereupon the pH adjustment then by treating the hydrolyzate with a hydroxide or carbonate of an alkali metal or of an alkaline earth metal is terminated. On the other hand, the pH of the wet precipitation can be in a certain Extent by treatment with, for example, sodium hydroxide are increased, followed by treatment with ammonia or an ammonium compound. In some cases it may be possible to add such an amount of the alkaline agent that the maximum prescribed amount of the treatment agent is exceeded, and then

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the proportion of this agent to a value within the specified area by draining or washing the To reduce precipitation. However, as already mentioned above explained, the washing at this stage is generally unfavorable, in particular because of the disadvantageous Effect on the flocculation state of the hydrolyzate.

Palls the pH of the precipitation does not fall to at least 6 is increased before calcination, the calcination step gives pigments with poor brightness and texture. The pH of the moist precipitate is preferably 7 immediately before calcination.

The incorporation of a total amount of at least '0.7 wt.% Of the ammonium compound or compounds, calculated as caused ammonium sulfate in the precipitate, that he is the aggregation before the calcination in a favorable state, so that the pigment formed is superior in opacity and has color strength. The presence of the ammonium compound or compounds before calcination also has the effect that the pigment is less aggregated and has a softer texture compared to pigments produced by conventional methods and the total proportion of the ammonium compound or compounds is advantageously at least 4.0% by weight .%, calculated as Ammoniumsulfab where these effects etc. are particularly striking.

In general, it has been found that at most little or no additional benefit is achieved when a total proportion of the ammonium compound or compounds above about 15% by weight, calculated as ammonium sulfab, is used.

Yortei-lha ft enough, there is the Aaimoniuni '/ Getting Connected from ammonium hydroxide or Ammoniumaarbonab "The Anmion.iuniver-

10 9-837 / * ^ p

BATH ORIGINAL

however, a bond can be formed in situ by ζ. Bo gaseous ammonia through a. aqueous slurry of the precipitation is directed »

The reason why the presence of the specified proportion of the ammonium compound or compounds before the calcination step improves the opacity KBd and the texture of the pigment formed is not entirely clear, but it seems likely that the favorable results are due to a combination of the effect of the ammonium compound or. -links on the state - the Aggre ™

P. gafcion of the hydrous © !! Titanium dioxides prior to calcination and the manner in which the ammonium compound or compounds are driven off in the course of the calcination may be attributed to s @ ia. It has been found that if © treated in 'according to the invention titanium dioxide lxydrolysat is calcined in a rotary kiln, decompose the ammonium compound or compounds check and be expelled from the titanium dioxide at relatively low! Temperatures, which takes place before any substantial conversion aes Hy & rolysats in Bu fei! Titanium dioxide has taken place »This decomposition and gas evolution can occur during the breakage of the

fe the drying formed lumps, which in these relatively takes place at low temperatures, support and the tendency of such lumps to confluence reduce hard aggregates *

If no ammonium compounds are incorporated into the precipitate before the calcination, the development and expulsion of the remaining sulfate or sulfuric acid takes place over a longer period of time and in a later stage of the process, if the aggregate already occurs in the initial & desrocknung ldSG have- which in the early £: / ifcu der Calcinie-

a 9 ö % 1

SAD ORIGINAL

It can all _t Eutil the formation-promoting seed materials are used and the inoculum can be added before or after the hydrolysis. An example of an inoculum that can be added prior to hydrolysis is the nucleated liquid obtained by diluting and then heating an acidic solution of a metal titanate, as described in British patent specification 623,813. An example of a seed material that can be added after hydrolysis is the seed material obtained by heating a mixture obtained by treating an alkali titanate with a monobasic acid and a titanium compound, as in US Pat. No. 2,389 026 described. If desired, both a pre-hydrolysis inoculum and a post-hydrolysis inoculum can be used. When the inoculum is added to the precipitate itself, the inoculum may be added any "any time" prior to calcination, but is preferably added after the washing process has started but before it is completed.

If the Eutil formation consists promotional inoculum from a compound of one of the elements "listed above as the treatment agent, must be taken to ensure that, taking into ä the herstammenden from the inoculum for the Eutil formation amount of supply of the prescribed maximum in the precipitate The amount of this element present immediately prior to calcination is not exceeded.

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■ feels like removing a drainage or washing treatment. . ■

It is important that the calcining conditions be carefully controlled during the period when the pigmentary properties are being developed, so as to ensure that the rate of growth of the rutile titanium dioxide particles does not become too high. Therefore, if the calcination is carried out in a conventional furnace, a relatively small amount of temperature rise in terms of time must be applied, so that a long rutilization zone and a relatively low maximum temperature result. Calcination for short periods of time at high temperatures leads to excessive particle growth, which in turn worsens the undertaking of the pigment obtained. The final stages of the conversion of anatase to rutile, ie from 90 % rutile upwards, take place relatively slowly during the calcination of the hydrolyzate which has been treated according to the invention, so that precise control of these important stages is facilitated.

The minimum required calcination temperature, lim the precipitate in the crystallographic form of the Conversion of rutile depends both on the specific treatment agents used and on the proportion of these means present in the precipitate immediately prior to calcination. In general, a rainfall requires which contains zinc or lithium as a treating agent does not have such high minimum calcining temperatures than required for a precipitate containing beryllium, magnesium, or aluminum treating agents is «Also the presence of potassium, rubidium or cesium treatments leads to an increase in the required minimum calcining temperature. Example

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BATH ORIGINAL

wise requires a precipitate that is 0.5 wt.% lithium oxide It contains a minimum temperature of 750 Ms 800 ° C, while a minimum! temperature of at least 950 ° C a precipitate is required which contains 0.5% by weight of aluminum oxide and 0.4% by weight of potassium oxide.

Advantageous combinations of the treatment agents include Magnesium and sodium treating agents, preferably 0.05 to 0.15 wt% magnesium and 0.1 to 0.5 wt% Sodium; Zinc and sodium treating agents, preferably from 0.05 to 0.25 percent zinc and 0.1 to 0.3 percent by weight sodium; and zinc and. Potassium treating agent preferably from 0.05 to 0.25% by weight zinc and from 0.05 to 0.25% by weight *

Potassium. All of the above percentages are calculated on the metal oxides and on the weight of the titanium dioxide based.

The pigmentary titanium dioxide particles produced according to the invention have a characteristic shape and contain a high proportion of well-formed crystals with clearly defined, straight edges. One special A favorable property of the finished pigments is that the parts also have a high proportion of Have needle-shaped crystals which make the pigment particularly useful for making paper opaque do. |

The proportion of the needle-shaped crystals in the pigment formed can be varied by changing the proportion of the treating agents can be varied within the specified ranges. In general, lowering the total proportion of the treatment agent or agents from the first group and an increase in the total proportion of the treatment agent or agents from the second group a favor of the formation of needle-shaped crystals. Especially good

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BATH

Results are obtained when the total proportion of the Treatment agent or the treatment agent from the first group does not exceed a value of 0.25% by weight and the total proportion of the treatment agent or agents from the second group is at least 0.2 Weight% is. If the total proportion of the treatment agent or agents from the first th group to a value above 0.5 wt.% Increased the advantageous crystalline properties are progressively lost.

Generally, it is stated that the presence of one or more lithium treating agents in the Precipitation immediately before calcination favors the formation of needle-shaped crystals and that increasing the amount of these agents results in an increase in the proportion of acicular crystals in the formed Pigment leads,

The formation of needle-shaped crystals is also caused by the relatively low speed of the. Rutile formation favors, for example, a rate of rutile formation that in a rotary kiln with a The extent to which the precipitation temperature increases by less than 1 ° G per day is caused.

The pigmentary titanium dioxide obtained by the calcination contains a proportion of sintered aggregates which have a tendency to deteriorate the pigmentary properties, but it was found that the number of crystals de aggregate in the pigment formed according to the invention is lower than in one according to the As a result, the potential soot-black undertone value (OBU) can be satisfactorily developed merely by rolling the pigment formed, while it is necessary to use both a Tvockm, -vrev: .ahlBt \ r £ Q as-well

BATH ORIGINAL

-. 15 -

to carry out an intensive wet milling step such as sand milling to satisfactorily adjust the undertone of a pigment prepared in the usual way.

Although a sand grinding to develop the undertone is not necessary, it is nevertheless advantageous to use a hate marriage process after the pigment formed To undergo calcination to obtain a pigment which after incorporation in a paint medium results in a paint with optimal gloss retention.

One advantage of the characteristic shape of the pigment particles obtained in accordance with the invention is in that these particles show a relatively low abrasion, which makes them very useful for breaking gloss of fibers and for use in printing inks. The particles also show a lower oil absorption value compared to pigments obtained by conventional methods.

The pigmentary titanium dioxides produced according to the invention can be subjected to a surface treatment before use or can be used untreated. Thus, the pigment may be used without surface treatment, it is necessary to reduce the similar content of water-soluble ingredients and for this! Purpose, the total content of the treatment agent from the second-listed group advantageously less than 0.2 wt.% If the content of water-soluble material of the pigment is not limited in this way or otherwise, the pigment has a tendency to disperse unsatisfactorily in the paint medium.

The pigment is preferably leached out before it is subjected to the surface treatment. It's beijoii-

109837/1676 _BA0 ORK31NM-

It is also important to use the leaching process before the surface treatment when the proportion, treatment agent or agents from the second. Group before calcination exceeds 0.4%. If lithium or a lithium compound is used as the treatment agent or as one of the treatment agents, it is preferred for economic reasons to leach out the finished pigment in order to partially recover the lithium. The resulting leach liquor can then be concentrated and used to treat fresh titanium dioxide hydrolyzate.

The invention also relates to paints, paints, enamels for plastic materials or elastomeric materials which contain a titanium dioxide pigment produced according to the invention. _;

The following examples serve to further illustrate the invention.

Example Λ

A titanium sulphate solution, which was obtained by digesting an Australian iltnenite in concentrated sulfuric acid and dissolving the digestion products in water, ₄ was treated with an iron file to reduce all of the dissolved iron to the ferrous form. The composition of the Australian ilmenite was as follows;

BATH ORIGINAL

Weight%

₂ 53.7

FeO 22.0

Fe ₂ O ₃ 20.1

Al ₂ O ₃ 0.51

₅
Cr ₂ O ₃ 0.03

₂₅ 0.1?

ZrO ₂ 0.1

MnO 1.5

An organic flocculant was then added and the resulting solution clarified to remove the undissolved material and cooled until the ferrous sulfate crystallized. A sufficient amount of the crystalline ferrous sulfate was removed to produce a Weight ratio of titanium dioxide: iron of about 3 »1 '* 1» 0. The concentration of titanium dioxide in the solution was then increased to 225 6 per liter by evaporation under reduced pressure, so that a titanium sulfate solution suitable for hydrolysis was obtained % By weight of cores for rutile induction, based on the weight of the titanium dioxide, which had been produced from a titanium tetrachloride solution, were equal to

added to this solution , which was then refluxed at constant volume for 3 hours to precipitate the water-containing titanium dioxide.

The hydrous titanium dioxide was ^then neutralized carefully to reduce the concentration of iron and other contaminants to as low a value as possible and washed was added to a pH of 7 »0 35 $ J-6 ammonia solution. After the neutralization step, the excess water was removed from the

«AD

Hydrolyzate filtered off, but no washing treatment agile. The filter cake obtained, which has a solids content of 35 »3% by weight and 11% by weight ammonium ions, ' calculated as ammonium sulfate and based on weight contained by TiOpι, was then divided into individual parts, which were treated in the following way:

0.4% by weight sodium sulfate, calculated as Na ^ O »and either 0.1% by weight or 0.5% by weight of a silicon, tin, Lithium, beryllium, calcium, zirconium, magnesium, aluminum, cadmium, bismuth or zinc compound, calculated as the oxide of the element, were added to each part. Except in the case of silicon, tin and bismuth each element is added in the form of a mixed solution of its sulfate with sodium sulfate.

The silicon was added in the form of a slurry of finely divided silica in the sodium sulfate ^{solution 1} } the tin was added in the form of a mixed solution of tin (II) chloride and sodium sulfate and the wis mut was added in the form of a suspension of bismuthyl nitrate in the sodium sulfate solution.

The treated portions of the neutralized titanium dioxide were then calcined for a period of 2 1/2 hours in a laboratory muffle furnace to obtain pigmentary titanium dioxide, 98 % of which was in the rutile form. In each case the calcination temperature was in the range from 780 to 1000 ° C, the exact temperature depending on the particular treatment agent used. So was z. B. the part of the hydrous titanium dioxide that had been treated with lithium sulfate / sodium sulfate, calcined at 780 ° C and the part that had been treated with aluminum sulfate / sodium sulfate "was calcined ^{at 950 ° G.}

The lightness of each sample of the pigment was below

10983771 & 2G

8ADORiGlNAL

Using a differential colorimeter, the brightness values of each pigment are determined according to the Chromatic value system according to Adams are given in the table below, which also shows the proportions of the Shows treating agent prior to calcination, all percentages being by weight. In the Adams system, "L" denotes the logarithmic Function of the brightness, based on a burned magnesium oxide surface, for the L = 100, whereby favorably get as high an "L" value as possible will.

'robe Precalcini inheritance % Na ₂ O Color brightness % Oxide 0.4 L-Vert 1 0.1 SiO ₂ 0.4 93.3 2 0.5 SnO ₂ 0.4 93.1 3 without • 0.4 93.4 4th 0.1 Li ₂ O 0.4 97.5 5 0.1 ¹ BeO 0.4 96.4 6th 0.5 CaO 0.4 93.1 7th 0.1 ZrO ₂ 0.4 92.9 8th 0.1 MgO 0.4 97.0 9 0.1 Al ₂ O ₅ 0.4 96.6 10 0.5 CdO 0.4 92.9 11 0.1 BiO 0.4 92.9 12th 0.1 ZnO 97.3

It can be seen from the table above that the brightness of the pigmentary material, which by Calcination of such parts of the neutralized hydrolyzate obtained, which with sodium sulfate and a compound of one of the elements beryllium, lithium, aluminum, Magnesium or zinc, as in samples 4, "5, 8, 9 and 12, is superior to that of a pigment obtained either by calcining the parts of the neutralized hydrolyzate, which is made with sodium sulfate and a compound of silicon * tin, cadmium, Bismuth ^ calcium or zircon (samples 1, 2, 6, 7, 1Ö and 11) or by lending the neutralized hydrolysate, soft only with sodium sulphate would receive.

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BATH ORIGINAL

Example 2

A titanium sulphate solution suitable for hydrolysis, which consists of a mixture of 3 parts by weight of Norwegian Ilmenite and 1 part by weight Australian ilmenite by the in the order of the stages given in Example 1, contained 215 g / l titanium dioxide, 75 g / l iron, 572 g / l sulfuric acid and 1.5 g / l trivalent titanium.

A nucleating seed material for the hydrolysis was made by diluting, neutralizing and subsequent heat treatment of a small proportion of the titanium sulfate solution and in the main part of the solution (| in an amount of 0.6% by weight, based on the weight of titanium dioxide, incorporated. After the inoculum treatment, the solution was on for 3 1/2 hours Heated reflux with constant volume, whereby the water-containing titanium dioxide precipitated.

The hydrous titanium dioxide precipitate was used extensively for reducing iron content and others Impurities to as low a level as possible washed, the washing being carried out with water, which was made weakly acidic with sulfuric acid in order to prevent the precipitation of any iron compounds impede.

Cores to initiate rutile formation were made from ™ part of the washed titanium dioxide hydrolyzate by digestion in caustic soda to form sodium titanate, Washing of the sodium titanate to remove the excess caustic soda and any sulphate present and subsequent peptization of the washed titanate made with hydrochloric acid.

An aqueous slurry with a titanium dioxide content of 250 g / l was made from the main part of the water

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produced and the inoculum for rutile formation in the aqueous slurry in an amount of 2% by weight, "based on the weight of Titanium dioxide, incorporated. The resulting seeded slurry was then divided into 14 parts which have been treated in the following way:

Part 1s An amount of a potassium sulfate solution equivalent to 0.43% by weight of potassium oxide based on titanium dioxide was incorporated into the slurry with good stirring. The slurry was then neutralized to pH 8.0 with a 35% ammonia solution and drained by filtration. The filter cake obtained had a solids content of 35 * 5 % and contained 15% by weight of ammonium ions, calculated as ammonium sulfate. Analysis of the filter cake indicated that 49 »8 % of the potassium sulfate had been removed by filtration. The filter cake was then calcined at 930.degree. C. for 3 hours in a muffle furnace, a pigmentary titanium dioxide being obtained, 98% of which was present in the cristenographic form of the EütiIs. Since there was no compound of beryllium, lithium, aluminum, magnesium or zinc in the filter cake immediately before calcination, the precalcination treatment used in Part 1 was outside the scope of the invention.

Part 2: A quantity of a mixed solution of magnesium sulphate and potassium sulphate, corresponding to 0 * 012 wt. Ψ

ν -.:..- M & g ^ siumoxid and 0,4 Gew, # Kftliümoxidv where ^ edeaf Percentage based on the weight of the titanium dioxide was added to the slurry added with thorough stirring.

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Ti 7 "W ί» ΙΙΙΙΙΪ: ■! '! E! ". Jl!

The slurry was then neutralized to pH 8.0 using a 20% ammonia solution and filtering the neutralized slurry to remove the excess water. The amounts of potassium and magnesium in the filter cake obtained were 0.01% by weight of magnesium oxide and 0.2% by weight of potassium oxide, based on titanium dioxide, and the proportion of ammonium ions corresponded to 14.5% by weight of ammonium sulfate, based on Titanium dioxide. The filter cake was then placed in a laboratory muffle furnace at 930 ° C. for 3 hours calcined and gave a pigmentary titanium dioxide, of which 9β, 4% in the crystallographic view Form of rutile templates.

■ Since the proportion of magnesium present in the filter cake immediately before calcination is below the ranges listed above, this precalcining treatment is outside of the scope of the invention.

Part 3 A mixed solution of potassium sulfate and one of the up to 155 sulphates of the metals from the table below 3 to 13 was added to each portion. In each case, the resulting slurry was adjusted to pH 8.0 using a 30% ammonia solution neutralized and then filtered to remove the excess of water * The filter cake were in a laboratory muffle furnace for 3 hours calcined and obtained pigmentary titanium dioxide. The following table shows the precalcination values for parts 3 to 13 for each of the metals, calculated as metal oxide and based on TiOg, the precalcination ratios of ammonium ions, calculated

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net as ammonium sulfate and based on _{FIG. 2} the calcining temperature used and the rutile content of the pigment formed can be seen.

part
No. Amount available (% by weight)
the calcination potassium
oxide ammonium
connect
dung as
(KH ₄ ) ₂ S0 ^ Galci-
kidney Rutile
salary Metal oxide 0.2 14.1 tempe-
rature
( ⁰ C) (Wt.%) 3 0.02 MgO 0.2 14.9 925 97.2 4th 0.046 MgO 0.25 15.5 920 98.0 5 0.5 MgO 0.2 15.5 890 97.6 6th 0.1 Al ₂ O ₃ 0.2 15.4 990 98.0 7th 0.1 BeO 0.2 14.8 870 96.0 8th 0.1 ZnO 0.2 15.1 840 97.8 9 0.01 Li ₂ O 0.2 14.4 900 97.0 10 0.025 Li ₂ ⁰ 0.2. 14.2 875 95.4 11 0.05 M ₂ O 0.2 15.2 855 96.6 12th 0.2 M ₂ O 0.1 15.6 820 98.2 15th 0.7 ZnO 780 98.6

Part 14ϊ A mixed solution of potassium sulfate and zinc sulfate was added to the slurry, which was then filtered to remove the excess of water. The amounts of potassium and zinc retained in the filter cake obtained corresponded to 0.09 % K ₂ O and 0.71% by weight ZnO. The filter cake was ealined at 790 ° C. for 3 hours in a laboratory muffle furnace and produced a pigmentary titanium dioxide, 98.8 % of which was in the rutile form. The brightness and color fastness of the pigment samples obtained from the 14 files result from the following table

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bark. The brightness is given according to the Adams system, as described in Example 1 and the color strength is according to the Eeynolds scale specified.

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OR / GihiAL INSPECTED

It turns out that in the comparison tests pigments obtained, d. H. the pigments obtained from parts 1, 2, 9-13 and 14, a poorer one Brightness and / or color strength compared to the pigments obtained from the remaining parts became.

Example 3

A titanium sulphate liquid suitable for hydrolysis, which had been obtained from Norwegian ilmenite by the sequence of stages described in Example 1, contained 225 g / l TiO ₂ , 71 g / l ferrous acid, 565 g / l sulfuric acid and 2.0 g / l l trivalent titanium. The composition of the Norwegian ilmenite was as follows:

Weight%

TiO ₂

FeO

Fe ₂ O ₅

44, 9 32, 9 13, 4th O, 55 0, 22nd ο, 06

Cr ₂ O ₃ ....

ZrO ₂ <0.1

MnO 0.3

A hydrolysis nucleation seed was prepared from a portion of this liquid by the process prepared according to Example 2 and the remainder of the liquid then as described in this example, in the presence hydrolyzed by 0.5% by weight of the nucleation material, so that water-containing titanium dioxide is obtained » became.

109837/1626

ORIGINAL INSPECTED

The water-containing titanium dioxide was washed and a portion of nuclei for the initiation of rutile formation was prepared from a portion of the washed hydrolyzate in the manner indicated in Example 2. 2% by weight, based on TiOg », of this inoculum for rutile introduction were then mixed with the main part of the washed hydrolyzate.

An amount of an aqueous magnesium sulfate solution containing 0.05 wt% of magnesium oxide, based on ^ iOp ^'s ^ ~ spoke., Was then added to the slurry of mixed with the seed material hydrolyzate. After the addition of the magnesium sulfate, the slurry was neutralized to pH 9.0 with a 20% ammonia solution and dehydrated by filtration. The filter cake obtained, which contained 0.05% by weight of magnesium compounds, calculated as MgO and based on TiOp, and 22% by weight of ammonium ions, calculated as ^ IH ^ ZpSO ^ and based on TiOp, was then divided into four parts. The portions were then washed with demineralized water, each portion being washed to a different extent, so that four samples each having a different ammonium content were obtained. An amount of a sodium chloride solution equivalent to 0.05% NapO, based on TiOp, was added to each of the washed samples and the samples then calcined at 860 ° G for 1 1/2 hours in a laboratory muffle furnace and pigmented titanium dioxide in the crystallographic form of rutile. The rutile content, the tinting strength and the texture of each pigment are given in the following table together with the proportions of the amounts of ammonium ions present immediately before the calibrating.

10 9837/1626

part Wt.% .Ammo % Rutile Pifcmentary product Pigment- ^i;
texture No. nium compound
than (NH ₄ ) _? SO ₄ ,
available
before the calci-
renation J color strength
(Reynolds
Scale) Soft and
friable 1 4.2 98.0 1550 quite
soft, light
grindable 2 1.1 98.4 1470 quite
soft, light
grindable 3 0.72 98.0 1460 relatively hard
and kora-
shaped 4th 0.6 98.2 1270

It turns out that both the color strength and the texture of the pigment formed is also disadvantageous by reducing that which was present before galcination Proportion of ammonium ions to a value below 0.7 wt.% Is influenced «.

Example 4

A titanium sulfate liquid suitable for hydrolysis, which had been obtained by digesting a mixture of equal parts of Norwegian and Australian ilmenite and then dissolving, reducing, clarifying, crystallizing, separating and evaporating according to the steps described in Example 1, contained 225 g / l TiO ₂ , 73 g / l Etsen-II, 1.9 g / l trivalent titanium and 575 g / l sulfuric acid. An inoculum for hydrolysis nucleus formation was prepared from a part 'of the liquid according to Example 2 and 0.5% by weight of this inoculum to the main part of the plus

109837/1626

sigkeit added, which then for 3 1/2 hours was heated to reflux at constant volume and hydrous titanium dioxide resulted.

The hydrous titanium dioxide was then washed with acidified water to reduce the concentration of iron and other impurities to as low a level as possible. After the washing treatment, an aqueous slurry of the hydrolyzate containing 3% by weight, based on TiO ₂ , of cores of a material for initiating the formation of Eutil, which had been prepared according to Example 2, was added as a seed material. The hydrolyzate treated with the inoculum was divided into three parts, each of which was subjected to a different precalcining treatment, and then calcined for 18 hours in an oil-fired rotary kiln. The treatments before calcination were as follows:

Part 1: A mixed solution of sodium sulfate and magnesium sulfate was added to the slurry with thorough stirring, and the slurry was then neutralized to pH 7 »0 by adding 35 # ammonia solution Festste ff content of about 35% had and sodium, magnesium and ammonium compounds corresponding to 0.35 wt, # Na ₂ O, 0.07 wt.% MgO and contained 11.2 Gew.5i (NH ^ ^ GSO, each Percentage based on TiOp. The maximum calcination temperature was 860 ° C. The form of the pigment obtained is shown in the diagram reproduced in Figure 1 of the accompanying drawing. *

feil [, Zt A mixed solution of zinc sulfate and potassium sulfate was added to the vigorously stirred slurry.

.109937 / 1620

ben, which was then neutralized to pH 7.0 with a 35% ammonia solution. The filter cake obtained when the neutralized slurry was dewatered had a solids content of 35.5% and contained potassium, zinc and ammonium compounds corresponding to 0.2% by weight of K ₂ O, 0.15% by weight of ZnO and 11.4% by weight. % By weight (NH ^) ₂ SO ₄ , the percentage being based on TiO _2. The maximum calcination temperature was 850 ° C. and the shape of the pigment obtained is shown in the electron micrograph shown in Fig. 2 of the accompanying drawing.

Part 3: A mixed solution of zinc sulfate and potassium sulfate was added to the well-stirred slurry, which was then dewatered by filtration. The received The filter cake contained 0.12% by weight of potassium, calculated as potassium oxide and based on titanium dioxide, and 0.8% by weight zinc, calculated as ZnO and based on

₂ The maximum calcination temperature was 840 ° G ^- and the shape of the pigment obtained is shown in the electron micrograph shown in FIG. 3.

The color strength and texture of each sample of the pigment results from the following table:

texture

part
No. Tinting strength
(Keynolds scale) 1 1730 CVl 1720 3 1550

very soft and friable, free of large lumps

rather soft and friable, free of large lumps

moderately hard, large number of existing lumps

109837/1626

2063872

The abrasion behavior of each sample of the pigment was determined in the following manner;

A dispersion was prepared containing the pigmentary titanium dioxide, crude castor oil and ethyl lactate in a weight ratio of 5? 3 ^: 6 contained. 2 ml of this dispersion was drawn up on a padding 0.63 cm thick and 2.5 cm in diameter, which was attached to one side of a metal disc with a diameter of 2.5 cm, which was on a central shaft, which was on the other side attached to the disc and extending perpendicular to the plane thereof. The shaft was then connected to a motor in such a way that the disk could be rotated in the horizontal plane and that a load could be applied to the disk by means of a weight attached to the top of the shaft. A brass plate of two inches square and of known weight was placed under and in contact with the surface of the mold. A load of 200 g was applied to the disk and the disk was then rotated at a constant speed for a period of 2 hours. At intervals of 30 minutes, the brass plate was cleaned and weighed and the felt disk was impregnated with an additional 1 ml of the dispersion before continuing. The table below shows the extent of the loss of the weights of the brass disk that was obtained with each pigment, this size being a measure of the abrasion ability; of the pigment.

109837/16 * 6

Part no. Weight loss

1 38 mg / hour

2 42 mg / hr

3 60 mg / hr

109837/1626

Claims (1)

Claims 1. Process for the production of pigmentary titanium dioxide, characterized in that a Ti.tansulfatlösung is hydrolyzed to form a precipitate of hydrous titanium dioxide, a die Inoculum to the solution that promotes rutile formation of the titanium sulfate and / or to the precipitate is incorporated, the precipitate is washed and then the washed precipitate with one or more of the treatment agents lithium, beryllium, Aluminum, magnesium, zinc, sodium, potassium, rubidium, cesium or compounds of these metals are treated, the precipitate with a total amount of at least 0.7% by weight of one or more ammonium compounds, calculated as ammonium sulfate and based on the weight of titanium dioxide, whereupon the precipitate is calcined, the pH of the moist precipitate in the range from 6 to 10 immediately before the Calcination is and the calcination is carried out at a temperature in the range of 750 "to 1000 ° C, and pigmentary titanium dioxide is obtained and the amount of the treatment agent or agents is such that in the precipitate immediately before calcination a Total amount of one or more of the agents beryllium, aluminum, magnesium, zinc and compounds of these metals, wherein the amount of each agent is calculated as a metal oxide, within a range of 0.02 to 0.50% by weight and based on the weight of the titanium dioxide is present and a total amount in the precipitate immediately prior to calcination of one or more of the agents Sodium, potassium, rubidium, cesium or compounds of these Metals, the amount of the agent (s) as alkali 109837/162 oxide is calculated to be within a range of 0.05 up to 1.0% by weight, based on the weight of the titanium dioxide, is present, with lithium and / or one or more lithium compounds in place of any or all of the treatment agents listed first Group and / or the second group listed can be. 2. The method according to claim 1, characterized in that that a compound of one of these metals is used as a treatment agent. 3. The method according to claim or 2, characterized in that, indicates that as a compound from the first group a sulfate, chloride, hitrate, oxychloride, basic Sulfate, oxide, hydroxide, formate, acetate, oxalate, metal alkyl or alkoxide is used. 4. The method according to claim 1 to 3 »characterized in that as a connection from the second listed Group and / or as a lithium compound a sulfate, nitrate, chloride, oxide, hydroxide, carbonate, bicarbonate, Acetate, oxalate, benzoate or alkoxide is used. 5. The method according to claim 1 to 4-, characterized in that that a water-soluble compound is used as the treatment agent. 6. The method according to claim 5 »marked thereby | net that the treatment agent or agents are added to the precipitate in the form of an aqueous solution. 7- method according to claim 6, characterized in that that more than one treatment agent is used and that the agent is added in the form of an aqueous mixed solution will. 8. The method according to claim 1 to 4, characterized in that that at least one treatment agent consists of a water-insoluble compound and this compound 109837/1626 or each such compound is thoroughly mixed into the precipitate prior to galcination. 9. The method according to claim 8, characterized in that that the mixing is carried out by means of a mixer, which has a high degree of shear during operation owns, 1.0. Method according to claim 9 »characterized in that an Erenkel screw is used as the mixer will. 11. The method according to claim 10, characterized in, that the treatment agent or agents are incorporated into an aqueous slurry of the precipitate will. 12. The method according to claim 1 to 11, characterized in that the total amount of the treatment agent or the treatment agent from the first group is in the range from 0.02 to 0.2% by weight. 13 * Method according to claim 1 to 12, characterized in that that the total amount of the treatment agent or agents from the second group im The range is from 0.1 to 0.6% by weight. 14. The method according to claim 1 to 11, characterized in that that the total amount of the treatment agent or agents from the first group is one Does not exceed a value of 0.25% by weight and the total amount of the treatment agent or agents of the second group is at least 0.2% by weight. 15. The method according to claim 1 to 14, characterized in that that the total amount of the treating agent or each treating agent is incorporated into the precipitate before any pH adjustment that may be required is performed. 16. The method according to claim 1 to 14, characterized in that 109837/1626 indicates that the total amount of treatment ■ means or any treating agent is incorporated into the precipitate, after any required pH adjustment has been carried out. 17 · The method according to claim 1 to 14, characterized in that the amounts of the treatment agent or the treatment agent in the precipitate both before and after performing any required pH adjustment are incorporated. 18. The method according to claim 1 to 1? » characterized in that an alkaline ammonium compound in \ is incorporated in the precipitate. 19. The method according to claim 18, characterized in that an amount of the alkaline ammonium compound necessary to achieve any necessary pH adjustment is sufficient, is incorporated. 20. The method according to claim 1 to 17 »characterized in that a pH adjustment that may be required at least partially by treating the precipitate with a non-ammoniacal, alkaline Means is carried out, the pH of the moist precipitate immediately before calcination and the total amount of ammonium compound or compound | fertilize and the treatment agent or agents has the range specified in claim 1. 21. The method according to claim 1 to 20, characterized in that the total amount of ammonium compound or compounds is at least 4% by weight. 22. The method according to claim 21, characterized in that the total amount has a value of 15 wt.% does not exceed. 23. The method according to claim 1 to 22, characterized in that that ammonium hydroxide and / or ammonium 109837-1626 carbonate to be incorporated into the precipitate " 24. The method according to claim 23 »characterized in that that ammonium hydroxide in the precipitate is incorporated. 25 · The method according to claim 1 to 24, characterized in that the incorporation of the ammonium compound takes place in the precipitate by the formation of the compound in situ. 26. The method according to claim 25 »characterized in that that the ammonium compound by introducing gaseous ammonia into an aqueous slurry of the precipitate is formed. 27 · The method according to claim 1 to 26, characterized in that the precipitate is an acid treatment is subjected. 28. The method according to claim 1 to 2? » characterized, that to reduce the concentration of any vanadium and / or chromium impurities a cleaning treatment is carried out before the hydrolysis will. 29. The method according to claim 1 to 28, characterized in that immediately before the calcination of excess of the liquid removed from the precipitate will. 30. The method according to claim 1 to 29 »characterized in that that the precipitate is calcined in a rotary kiln and the extent of the increase in temperature of precipitation is less than 1 ° P per minute. 31. The method according to claim 1 to 30 »characterized in that that after calcination, the pigment formed is subjected to a wet milling process. 32. The method according to claims 1 to 31 »thereby 109897/1626 indicates that that formed by the calcination Pigment is subjected to a surface treatment. 33. The method according to claim 32, characterized in that that the pigment is leached out prior to surface treatment. , 34. The method according to claim 1 to 33> characterized in that lithium or an idthium compound is used as at least one treatment agent and the pigment obtained in the calcination is leached out. 35 · The method according to claim 34 »characterized in that that the leach liquor is concentrated and then used as a treatment agent for fresh titanium dioxide hydrolyzate is used. 36. The method according to claim 1 to 35 »characterized in that that the pH of the moist precipitate reached a value of 7 immediately before calcination owns. 37 · The method according to claims 1 to 36 »characterized in that that the precipitate with Hagnesiumu and / or a magnesium compound and with sodium and / or a sodium compound. 38. The method according to claim 37 »characterized in that immediately before the calcination in the precipitate an amount of 0.05 to 0.15 wt.% Of a magnesium treatment agent, calculated as MgO and based on TiOg, and 0.1 to 0.3 wt .% of a sodium treatment agent, calculated as Na ₂ O and based on TiOo, is present. 39 · The method according to claims 1 to 36, characterized in that that the precipitate with zinc and / or with a zinc compound and with sodium and / or with a sodium compound is treated. 109837/1626 40. The method according to claim 39 »characterized in that that immediately before calcination in the precipitate 0.05 to 0.25% by weight of a zinc treatment agent, calculated as ZnO and based on TiOo, and 0.1 to 0.3% by weight of a sodium treating agent, calculated as NapO and based on! M ^. 41. The method according to claim 1 to 36, characterized in that that the precipitate with zinc and / or a zinc compound and with potassium and / or a potassium compound is treated. 42. The method according to claim 41, characterized in that that immediately before calcination in the precipitate 0.05 to 0.25% by weight of a zinc treatment agent, calculated as ZnO and based on T1O2, and 0.05 to 0.25% by weight of a potassium treatment agent, calculated as KpO and based on TiOp, is present. 43. The method according to claim 1 to 36, characterized in that immediately before the calcination in the precipitate 0.5% by weight of an aluminum treatment agent, calculated as A ^ O ^ and based on TiOp, and 0.4% by weight of a potassium treatment agent, calculated as K ^ O and based on T1O2, are present and the precipitate is calcined at a temperature of at least 950 ° C. 44. The method according to claim 1 to 36, characterized in that that the treatment agent or agents from the second group of sodium or a sodium compound exist. 4-5 · Method according to claim 1 to 36, characterized in that that the only treatment agent incorporated into the precipitate is lithium and / or one or more lithium compounds. 4-6. Method according to claim 1 to 45, characterized in that 109837 / T6-26 indicates that an inoculum to be used prior to hydrolysis is used to promote rutile formation will. 47 · The method according to claim 1 to 45, characterized characterized in that a to be used after the hydrolysis Inoculum that promotes rutile formation is used. 48. The method according to claim 47, characterized in that the inoculum to form the Rutile preferential treatment in the loft after the beginning of the Vaschver procedure, but incorporated before its completion will. 49. The method according to claim 1 to 45, characterized in that that both an inoculum before hydrolysis and an inoculum after hydrolysis for Favoring the rutile formation can be added. 50. Pigmentary titanium dioxide, produced according to a method of claims 1 to 49 51. Use of a titanium dioxide, produced according to one of claims 1 to 49 ₅ or according to claim 5o, for pigmenting paint, plastic, enamel or elastomeric material. 109837/1626 BATH ORIGINAL Lee rs e ι te